Blade and image forming apparatus incorporating same

ABSTRACT

An elastic blade may include an edge layer and at least one backup layer laminated on the edge layer. The edge layer may include a contact edge to contact a contact object and an opposing face to oppose the contact object, and the backup layer may be greater in elastic power than the edge layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 14/857,955, filed onSep. 18, 2015, which claims priority to and incorporates by referencethe entire contents of Japanese Patent Application No. 2014-214335,filed on Oct. 21, 2014, and Japanese Patent Application No. 2014-244926,filed on Dec. 3, 2014, in the Japan Patent Office, the entire disclosureof each of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

Embodiments of an example invention generally relate to a blade and animage forming apparatus, such as a copier, a printer, a facsimilemachine, or a multifunction peripheral (or multifunction machine) havingat least two of copying, printing, facsimile transmission, plotting, andscanning capabilities, that includes the blade.

Description of the Related Art

In electrophotographic image forming apparatuses, after a toner image istransferred from a surface of an image bearer such as a photoconductoronto a transfer sheet or an intermediate transfer member, a cleaningdevice removes toner remaining on the surface of the image bearer.

Cleaning devices employing a cleaning blade are widely used forsimplicity in structure and high cleaning capability.

SUMMARY

Example embodiments provide an elastic blade that includes an edge layerand at least one backup layer laminated on the edge layer. The edgelayer includes a contact edge to contact a contact object and anopposing face to oppose the contact object, and the backup layer isgreater in elastic power than the edge layer

In yet another example embodiment, an image forming apparatus includes acharger to charge a surface of an image bearer, an exposure device toexpose the surface of the charged image bearer to form an electrostaticlatent image thereon, a developing device to develop the latent imagewith toner into a toner image, a transfer device to transfer the tonerimage onto a recording medium, a fixing device to fix the toner image onthe recording medium, and a cleaning device to remove toner from theimage bearer. The cleaning device includes the blade described above.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view of a cleaning blade according to anexample embodiment;

FIGS. 2A and 2B are illustrations of vibration of an edge of asingle-layer cleaning blade;

FIG. 3 is a graph of cumulative stress caused while a Vickers penetratoris pushed in, and cumulative stress in removal of a test load;

FIG. 4 is an illustration of measurement of elastic power and Martenshardness of an edge of the cleaning blade according to an exampleembodiment;

FIG. 5 is a schematic diagram of an image forming apparatus according toan example embodiment;

FIG. 6 is a schematic cross-sectional view illustrating a processcartridge installable in the image forming apparatus illustrated in FIG.5;

FIG. 7 is a schematic cross-sectional view illustrating another processcartridge installable in the image forming apparatus illustrated in FIG.5;

FIG. 8 is a schematic cross-sectional view illustrating another processcartridge installable in the image forming apparatus illustrated in FIG.5;

FIGS. 9A through 9D are cross-sectional views of layer structuresapplicable to a photoconductor according to an example embodiment;

FIGS. 10A and 10B are illustrations of measurement of circularity oftoner; and

FIGS. 11A, 11B, and 11C are illustrations of wear of the single-layercleaning blade.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In describing preferred embodiments illustrated in the drawings,specific terminology is employed for the sake of clarity. However, thedisclosure of this patent specification is not intended to be limited tothe specific terminology so selected, and it is to be understood thateach specific element includes all technical equivalents that operate ina similar manner and achieve a similar result.

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views thereof,and particularly to FIG. 1, a blade according to an embodiment of anexample invention is described.

FIG. 1 is a cross-sectional view of a cleaning blade 5, serving as ablade according to an example embodiment.

The cleaning blade 5 illustrated in FIG. 1 is elastic. As illustrated inFIG. 1, a support 3 supports a base end of the cleaning blade 5 suchthat an edge 61, which is a ridgeline or a corner at an end opposite thebase end, abuts or contacts a surface of an object to be cleaned by thecleaning blade 5 (hereinafter “contact object”). The cleaning blade 5 isdouble-layered and includes an edge layer 6, which includes the edge 61,and a backup layer 7 laminated on the edge layer 6. In FIG. 1, referencenumeral 62 represents an opposing face positioned opposing the contactobject, and 63 represents an end face adjoining the opposing face 62 viathe edge 61.

The edge layer 6 and the backup layer 7 are made of elastic materialsdifferent in elastic power from each other. In an example embodiment,the backup layer 7 is made of urethane rubber higher in elastic powerthan the material of the edge layer 6, and the backup layer 7 is greaterin thickness than the edge layer 6.

There are single-layer cleaning blades made of polyurethane rubber lowerin hardness and having an elastic power of about 90% at or around theedge and a Martens hardness of about 0.7 N/mm². If a material lower inelastic power is used for such single-layer cleaning blades, indeformation of the cleaning blade upon application of force, the rate ofplastic deformation is greater than the rate of elastic deformation. Ifthe rate of plastic deformation is greater than the rate of elasticdeformation, the cleaning blade fatigues, and the cleaning capability isreduced.

In an example embodiment, the cleaning blade 5 is multilayered andincludes the edge layer 6 and the backup layer 7, and the backup layer 7is higher in elastic power than the edge layer 6. With thisconfiguration, regarding plastic deformation caused by force of bendingor compression applied to the cleaning blade 5, the amount of plasticdeformation of the backup layer 7 is smaller than the amount of plasticdeformation of the edge layer 6. Additionally, in an example embodiment,the edge layer 6 and the backup layer 7 affect, at identical or similardegrees per unit thickness, deformation of the entire cleaning blade 5,and the backup layer 7 is thicker than the edge layer 6. Accordingly,deformation of the backup layer 7 is dominant in deformation of theentire cleaning blade 5. Accordingly, fatigue of the entire cleaningblade 5 is suppressed by keeping the amount of plastic deformation ofthe backup layer 7 smaller than the amount of plastic deformation of theedge layer 6.

Additionally, when a single-layer cleaning blade is made of a materialhigher in elastic power, micro vibration arises at the edge of thecleaning blade due to the sliding between the cleaning blade and thecontact object. It is possible that the vibration at the edge coincideswith an eigenfrequency of the cleaning blade and grows, causing noise.

In the cleaning blade 5 according to an example embodiment, the edgelayer 6, which includes the edge 61 to contact the contact objectdirectly, is lower in elastic power than the backup layer 7. With thisstructure, when the vibration of the edge layer 6 is about to grow, thebackup layer 7 is capable of isolating vibration. Specifically, sincethe backup layer 7 is contactless with the contact object and made ofthe material higher in elastic power than the edge layer 6, the backuplayer 7 absorbs vibration and serves as a vibration isolator.Accordingly, the backup layer 7 suppresses the occurrence of noiseinherent to micro vibration of the edge 61 caused by the sliding withthe contact object.

FIGS. 2A and 2B are illustrations of a single-layer cleaning blade knownto the inventors, as a comparative example.

Referring to FIG. 2A, an edge 261 of a cleaning blade 105 abuts orcontacts a surface of a contact object 110 that moves in the directionindicated by arrow Y1, and the edge 261 vibrates at that time.

Elastic power is one index of ease of recovery from deformation ofrubber when the rubber is deformed with force. If the cleaning blade 105is higher in elastic power, the edge 261 recovers at a high speed fromdeformation due to the contact with the contact object 110. Then, asillustrated in FIG. 2B, the edge 261 of the cleaning blade 105 vibratesat a high speed. Accordingly, the vibration of the edge 261 is morelikely to coincide with the eigenfrequency of the cleaning blade 105,and the vibration causes noise more easily.

In the cleaning blade 5 according to an example embodiment, the edgelayer 6 is lower in elastic power than the backup layer 7. With thisstructure, the backup layer 7 absorbs the vibration caused bydeformation of the edge layer 6, and the vibration frequency of the edgelayer 6 less easily coincides with the eigenfrequency of the cleaningblade 5. Accordingly, the occurrence of vibration inherent in recoveryfrom deformation of the edge 61 is inhibited.

When the material lower in elastic power is used for the single-layercleaning blade, the cleaning blade plastically deforms in a greateramount upon application of force of bending or compression. By contrast,when a material higher in elastic power is used for the single-layercleaning blade, although the fatigue is inhibited, vibration of the edgeof the blade results in noise (chatter). Thus, it is difficult toinhibit both of fatigue of the blade and noise of the blade in thesingle-layer cleaning blade. Additionally, in multilayer blades, it ispreferred to define the relation between the elastic power of the edgelayer 6 and that of the backup layer 7 to extend the operational life ofthe cleaning blade and enhance reliability.

In the multilayer cleaning blade 5, making the backup layer 7 greater inelastic power than the edge layer 6 is advantageous in suppressing theoccurrence of noise caused by sliding between the edge of the blade andthe contact object and inhibiting fatigue of the blade with elapse oftime.

It is to be noted that the difference in elastic power between the edgelayer 6 and the backup layer 7 is preferably about from 5% to 50%.

If the difference in elastic power between the edge layer 6 and thebackup layer 7 is less than 5%, the difference is too small. In thiscase, the blade fatigues more easily as the elastic power of thecleaning blade 5 decreases, and noise arises more easily as the elasticpower of the cleaning blade 5 increases.

If the difference in elastic power between the edge layer 6 and thebackup layer 7 is greater than 50%, inevitably the elastic power of theedge layer 6 is lower. Accordingly, cleaning capability is more likelyto decrease due to the plastic deformation of the edge 61.

Although the description above concerns the double-layer cleaning blade5 including the edge layer 6 and the backup layer 7, aspects of anexample specification are not limited thereto. For example, aspects ofan example specification include a structure in which the backup layer 7is multilayered.

Additionally, although the backup layer 7 is made of urethane rubberhigher in elastic power than the edge layer 6 in the description above,aspects of an example specification are not limited thereto. As long asthe backup layer 7 is higher in elastic power than the edge layer 6,similar effects are available in cases where materials other thanurethane rubber are used.

When the backup layer 7, which is higher in elastic power (less easilydeforms plastically), is thicker than the edge layer 6, the backup layer7 is dominant in deformation of the entire cleaning blade 5, and thebackup layer 7 inhibits fatigue of the cleaning blade 5. It is to benoted that, if the edge layer 6 is extremely thin, as the edge layer 6wears due to sliding with the contact object, the backup layer 7 isexposed early. Then, the backup layer 7 higher in elastic power contactsthe contact object and causes noise. Accordingly, it is preferred thatthe edge layer 6 have a thickness sufficient for preventing exposure ofthe backup layer 7 even when the edge layer 6 wears.

Next, experiment to verify the effects of an example embodiment aredescribed below.

Experiment 1

In Experiment 1, cleaning blades different in layer structure, elasticpower, and Martens hardness were evaluated.

[Elastic Power]

The elastic power of the edge 61 of the cleaning blade 5 was measuredusing a micro hardness measuring system, FISCHERSCOPE® HM2000, fromFischer Technology, Inc, as follows. Push a Vickers penetrator in thecleaning blade 5 at 20 μm from the edge (ridgeline), with a strength of1.0 mN for 10 seconds, keep that state for 5 seconds, and graduallydraws out the Vickers penetrator in 10 seconds. Then, measure theelastic power.

The elastic power is a characteristic value defined asW_(elast)/W_(plast)×100%, wherein W_(plast) represents the cumulativestress caused while the Vickers penetrator is pushed in, and W_(elast)represents cumulative stress caused in removal of the test load (seeFIG. 3). FIG. 3 is a graph of the cumulative stress Wplast while theVickers penetrator is pushed in, and the cumulative stress Welast inremoval of the test load. In FIG. 3, the abscissa represents the amountby which the penetrator is pushed in (i.e., pushing-in amount), theordinate represents the strength of the force.

As the elastic power increases, the rate of plastic power in the periodfrom application of force to distort the material to remove the loadbecomes smaller. That is, the rate of plastic deformation of rubberdeformed by force is smaller.

FIG. 4 is an illustration of measurement of the elastic power and theMartens hardness of the edge layer 6 of the cleaning blade 5.

As illustrated in FIG. 4, the cleaning blade 5 includes the opposingface 62 including the edge 61, and the end face 63 including the edge 61and adjoining the opposing face 62. The opposing face is disposedopposing the contact object.

In the double-layer cleaning blade 5, if the edge layer 6 is extremelythin relative to the backup layer 7, it is possible that the measuredelastic power is affected by the elastic power of the backup layer 7when the elastic power of the edge layer 6 is measured from the opposingface 62.

For example, in measurement of the elastic power of the edge layer 6lower than the elastic power of the backup layer 7, if affected by theelastic power of the backup layer 7, the measurement value of elasticpower of the edge layer 6 is higher than the measurement value obtainedby measuring the elastic power of the material used for the edge layer 6alone.

The inventors have found that, even if the edge layer 6 is extremelythin relative to the backup layer 7, the elastic power of the edge layer6 can be measured with a higher degree of accuracy in the followingmethod.

Referring to FIG. 4, define the elastic power of the edge layer 6measured from the opposing face 62 (in the direction indicated by arrowEa) as Elastic power A, define the elastic power of the edge layer 6measured from the end face 63 (in the direction indicated by arrow Eb)as Elastic power B, and define the elastic power of the backup layer 7measured from the end face 63 (in the direction indicated by arrow Ec)as Elastic power C. Calculate the difference between Elastic power A andElastic power C, and that between Elastic power B and Elastic power C.Then, determine, the greater of Elastic power A or Elastic power B inabsolute value of the difference with Elastic power C, as the elasticpower of the edge layer 6. That is, when the absolute value of thedifference between Elastic power A and Elastic power C is greater thanthe difference between Elastic power B and Elastic power C, Elasticpower A is defined as the elastic power of the edge layer 6. When thedifference between Elastic power B and Elastic power C is greater thanthe difference between Elastic power A and Elastic power C, Elasticpower B is defined as the elastic power of the edge layer 6.

Table 1 shows the elastic power measured by this method.

Descriptions are given below of the configuration of the image formingapparatus used in the experiments and evaluation items.

(Cleaning Capability Under Cool and Dry Conditions)

In the experiment, a Ricoh image forming apparatus, MP C3503, was usedas a test machine, and the cleaning blade 5 of a process cartridge 121illustrated in FIG. 6 was replaced with those according toConfigurations 1 through 14 and Comparative examples 1 through 10.

Under cool and dry (low temperature and low humidity) conditions,defective cleaning is likely to occur. After the test machine was leftunused for 24 houses under low temperature (10° C.) and low humidity(15%) conditions, images were output on 80,000 sheets consecutivelyunder the temperature of 10° C. and the humidity of 15%. To input agreater amount of toner to a photoconductor (image bearer), a solidimage extending entirely A4 size was input. The output sheets werechecked for a trace of defective cleaning with eyes and evaluated asfollows.

Good: Cleaning capability is good. After output of 80,000 sheets, thetrace of defective cleaning is not observed on the sheets, andpractically there are no problems.

Defective: The trace of defective cleaning is visible. After output of80,000 sheets, the trace of defective cleaning is observed on thesheets, and practically the outputs images are deemed substandard.

(Noise)

The Ricoh image forming apparatus, MP C3503, was used as the testmachine, and the cleaning blade 5 of the process cartridge 121illustrated in FIG. 6 was replaced with those according toConfigurations 1 through 14 and Comparative examples 1 through 10.

Using the test machine, 40,000 sheets of A4 size were consecutively fedunder a temperature of 23° C. and a humidity of 50% as ordinary roomconditions, and an image having an image area ratio of 5% (an averageimage area ratio in use of products) was printed. While the sheets werefed, the occurrence of noise was checked with ears and evaluated asfollows.

None: No noticeable noise in feeding of 40,000 sheets.

Occurred: Noticeable noise is recognized in feeding of 40,000 sheets.

(Fatigue of Blade)

The Ricoh image forming apparatus, MP C3503, was used as the testmachine, and the cleaning blade 5 of the process cartridge 121illustrated in FIG. 6 was replaced with those according toConfigurations 1 through 14 and Comparative examples 1 through 10.

Using the test machine, the blade edge contact pressure was measuredbefore and after the cleaning blade was kept in contact with the imagebearer for seven days (168 hours) under a temperature of 23° C. and ahumidity of 50% (ordinary room conditions). The cleaning blade was keptin contact with the image bearer, and changes in contact pressureoccurring by keeping the cleaning blade under the pressure wereevaluated. The contact pressure with which the cleaning blade contactsthe image bearer was 20 g/cm.

Effects of fatigue of the cleaning blade on the cleaning capability wereevaluated as follows under a condition of high charging current.

Not affected: Reduction in line pressure is smaller than 4.0 g/cm (20%of line pressure setting). No effects on the cleaning capability.

Affected: Reduction in line pressure is equal to or greater than 4.0g/cm (20% of line pressure setting). Cleaning capability was affected.

Evaluation results of configurations according to an example embodimentand the comparative examples are shown in Table 1 below. In Table 1, E1through E14 represents Configurations 1 through 14, and C1 through C10represents Comparative examples 1

TABLE 1 Elastic Cleaning Fatigue of blade power (%) capability LineBlade Back- under cool Effects pressure struc- Edge up and dry on changeture layer layer conditions cleaning (g/cm) Noise E1 Double 82 91 GoodNot 2.3 None layer affected E2 Double 79 85 Good Not 2.6 None layeraffected E3 Double 75 81 Good Not 3.1 None layer affected E4 Double 7289 Good Not 2.8 None layer affected E5 Double 69 92 Good Not 2.1 Nonelayer affected E6 Double 67 85 Good Not 2.3 None layer affected E7Double 65 87 Good Not 2.8 None layer affected E8 Double 62 82 Good Not3.0 None layer affected E9 Double 58 92 Good Not 2.6 None layer affectedE10 Double 52 85 Good Not 3.2 None layer affected E11 Double 48 71 GoodNot 3.1 None layer affected E12 Double 46 80 Good Not 3.2 None layeraffected E13 Double 43 75 Good Not 3.3 None layer affected E14 Double 4070 Good Not 3.5 None layer affected C1 Single 92 Good Not 3.9 Oc- layerobserved curred C2 Single 38 Defec- Affected 5.9 None layer tive C3Double 92 68 Defec- Affected 5.2 Oc- layer tive curred C4 Double 87 59Defec- Affected 5.6 Oc- layer tive curred C5 Double 82 52 Defec-Affected 5.8 Oc- layer tive curred C6 Double 78 48 Defec- Affected 6.5Oc- layer tive curred C7 Double 30 80 Defec- Not 3.0 None layer tiveaffected C8 Double 35 85 Defec- Not 2.2 None layer tive affected C9Double 39 60 Defec- Affected 5.9 None layer tive C10 Double 30 50 Defec-Affected 6.5 None layer tive

(Configuration 1)

In Configurations 1 (E1 in Table 1), the double-layer cleaning blade 5including the edge layer 6 (0.5 mm in thickness) and the backup layer 7(1.3 mm in thickness) illustrated in FIG. 1 was used.

In Configuration 1, the elastic power of the edge layer 6 is 82%, andthe elastic power of the backup layer 7 is 91%, which is higher thanthat of the edge layer 6.

In Configuration 1, regarding the fatigue evaluation, the line pressurewas reduced by 2.3 g/cm while the cleaning blade 5 was kept in contactwith the image bearer (contact object) for 168 hours. The line pressurereduction of Configuration 1 is smaller than a specified line pressurereduction of 4.0 g/cm (20% of line pressure setting), which is deemed tocause defective cleaning in MP C3503. The line pressure reduction ofConfiguration 1 did not affect the cleaning capability.

It is conceivable that the fatigue to cause defective cleaning isinhibited as follows.

In Configuration 1, since the backup layer 7 is higher in elastic powerthan the edge layer 6, the amount of plastic deformation of the backuplayer 7, which arises when the cleaning blade 5 is bent or compressedwith force, is smaller than the amount of plastic deformation of theedge layer 6. In Configuration 1, the edge layer 6 and the backup layer7 are identical or similar to each other in the degree of effect, perunit thickness, on deformation of the entire cleaning blade 5, and thebackup layer 7 is thicker than the edge layer 6. Accordingly,deformation of the backup layer 7 is dominant in deformation of theentire cleaning blade 5. Accordingly, fatigue of the entire cleaningblade 5 is suppressed by keeping the amount of plastic deformation ofthe backup layer 7 smaller than the amount of plastic deformation of theedge layer 6.

Additionally, in Configuration 1, since the edge layer 6, which includesthe edge 61 to contact the contact object directly, is lower in elasticpower than the backup layer 7, when the vibration of the edge layer 6 isabout to grow, the backup layer 7 exhibits vibration isolatingcapability. Accordingly, the occurrence of noise inherent to microvibration of the edge 61, which is caused by the sliding with thecontact object, is inhibited.

Further, since the edge layer 6 is lower in elastic power than thebackup layer 7, the backup layer 7 absorbs the vibration caused bydeformation of the edge layer 6, and the vibration frequency of the edgelayer 6 less easily coincides with the eigenfrequency of the cleaningblade 5. Accordingly, the occurrence of vibration inherent in recoveryfrom deformation of the edge 61 is inhibited.

(Configurations 2 through 14)

In the cleaning blades 5 according to any of Configurations 2 through14, the elastic powers of the edge layer 6 and the backup layer 7 aredifferent from those of Configuration 1 as shown in Table 1, and thebackup layer 7 is greater in elastic power than the edge layer 6 similarto Configuration 1. In any of Configurations 2 through 14, theoccurrence of noise caused by the sliding between the edge 61 of thecleaning blade 5 and the contact object was inhibited, and the fatiguewith elapse of time was inhibited. The reason of such an evaluationresult is similar to that of Configuration 1, and thus the descriptionis omitted.

Comparative Example 1

Differently from the multilayer cleaning blade 5 according toConfigurations 1 through 14, the cleaning blade according to Comparativeexample 1 is single-layered, and the elastic power of the single-layercleaning blade is 92%, which is greater than the elastic power of theedge layer 6 in Configurations 1 through 14.

Since the material higher in elastic power was used for the single-layercleaning blade, the edge of the cleaning blade vibrated (microvibration) due to the sliding with the photoconductor. The vibrationfrequency of the edge coincided with the eigenfrequency of the cleaningblade, and noise occurred.

Since the elastic power was higher, the speed of vibration increased,increasing the possibility of occurrence of noise.

Comparative Example 2

Differently from the multilayer cleaning blade 5 according toConfigurations 1 through 14, the cleaning blade according to Comparativeexample 2 is single-layered. The line pressure was reduced by 5.9 g/cmafter the single-layer cleaning blade was kept in contact with thephotoconductor for 168 hours. This reduction in line pressure is greaterthan the specified line pressure reduction of 4.0 g/cm (20% of linepressure setting), which is deed to cause defective cleaning in MPC3503. This reduction in line pressure reduction degraded the cleaningcapability. The elastic power of the single-layer cleaning blade ofComparative example 2 is 38%, which is smaller than the elastic power ofthe cleaning blade 5 in Configurations 1 through 14.

Since the material lower in elastic power was used for the single-layercleaning blade of Comparative example 2, when the cleaning blade isdeformed (bent or compressed) by force, the rate of plastic deformationis greater than the rate of elastic deformation. It is conceivable thatthe cleaning blade fatigued and the cleaning capability was reduced.When the blade fatigues, the line pressure of the cleaning blade to thecontact object decreases, or the position or posture of the cleaningblade changes, resulting in defective cleaning.

Comparative Example 3

The cleaning blade used in Configuration 3 is double-layered andincludes the edge layer 6 and the backup layer 7, similar to thecleaning blade 5 illustrated in FIG. 1. The edge layer 6 is 0.5 mm andthe backup layer 7 is 1.3 mm in thickness. The edge layer 6 has anelastic power of 92%, and the backup layer 7 has an elastic power of68%, and thus the backup layer 7 is lower in elastic power than the edgelayer 6, differently from Configurations 1 through 14.

The line pressure was reduced by 5.2 g/cm after the cleaning blade waskept in contact with the photoconductor for 168 hours. This reduction inline pressure is greater than the specified line pressure reduction of4.0 g/cm (20% of line pressure setting), which causes defective cleaningin MP C3503. This reduction in line pressure reduction degraded thecleaning capability.

In the cleaning blade according to Comparative example 3, the backuplayer 7 is lower in elastic power than the edge layer 6. In Comparativeexample 3, the edge layer 6 and the backup layer 7 is identical orsimilar to each other in the degree of effect per unit thickness on thedeformation of the entire cleaning blade. The backup layer 7 is thickerthan the edge layer 6. Accordingly, deformation of the backup layer 7 isdominant in deformation of the entire cleaning blade. That is, theamount of plastic deformation of the backup layer 7 is greater than theamount of plastic deformation of the edge layer 6. Accordingly, theentire cleaning blade 5 fatigued, and the line pressure decreased,resulting in defective cleaning.

In the cleaning blade according to Comparative example 3, the edge layer6 is made of the material higher in elastic power than that of thebackup layer 7. When the edge of the cleaning blade vibrates (microvibration) due to the sliding with the photoconductor, the backup layer7 does not isolate vibration since the backup layer 7 is lower inelastic power than the edge layer 6. Accordingly, in Comparative example3, the vibration of the edge coincided with the eigenfrequency of thecleaning blade more easily, and the vibration caused noise.

Additionally, if the edge layer 6 is higher in elastic power than thebackup layer 7, the edge recovers at a higher speed from deformation dueto the contact with the photoconductor, and the edge vibrates at ahigher speed. Accordingly, in Comparative example 3, the vibration ofthe edge coincided with the eigenfrequency of the cleaning blade moreeasily, thereby increasing the possibility of noise caused by vibrationinherent to recovery from deformation.

Comparative Examples 4 Through 6

The cleaning blades used in any of Comparative examples 4 through 6 isdifferent from that of Comparative example 3 only in the elastic powersof the edge layer 6 and the backup layer 7 as shown in Table 1.

The backup layer 7 is lower in elastic power than the edge layer 6,differently from Configurations 1 through 14. Accordingly, inComparative examples 4 through 6, the line pressure decreased to causedefective cleaning, and noise occurred due to the sliding between thephotoconductor and the edge of the cleaning blade. The reason of thisevaluation is similar to that of Comparative example 3, and thus thedescription is omitted.

Comparative Examples 7 and 8

In the cleaning blade used in Comparative example 7 or 8, the backuplayer 7 is higher in elastic power than the edge layer 6 similar toConfigurations 1 through 14. Accordingly, similar to Configuration 1,the fatigue of the cleaning blade and noise were inhibited.

However, the elastic power of the edge layer 6 is smaller than 40%.Accordingly, micro plastic deformation of the edge of the cleaning bladeoccurred, and a greater amount of toner and external additives to tonerescaped from a gap at the nip between the edge and the photoconductor(contact object). The escaped toner and the additives abraded the edgeof the cleaning blade, and the cleaning capability under cool and dryconditions was degraded.

Comparative Examples 9 and 10

In the cleaning blade according to Comparative example 9 or 10, theelastic power of the backup layer 7 is smaller than 70%. If the elasticpower of the backup layer 7 is smaller than 70%, the backup layer 7plastically deforms by bending stress. In the double-layer cleaningblade, the backup layer 7 is greater in thickness than the edge layer 6,and deformation of the backup layer 7 is dominant in deformation of theentire cleaning blade. Accordingly, in Comparative examples 9 and 10,the entire cleaning blade fatigued, and the line pressure decreased,resulting in defective cleaning.

From the evaluation results shown in Table 1, the elastic power of theedge layer 6 is preferably equal to or greater than 40%.

By setting the elastic power of the edge layer 6 to 40% or greater,defective cleaning caused by plastic deformation of the edge 61 isinhibited. If the elastic power of the edge layer 6 is smaller than 40%,as described with reference comparative examples 7 and 8, micro plasticdeformation of the edge 61 of the cleaning blade 5 occurs. Then, agreater amount of toner and external additives to toner escape from thegap at the nip between the edge 61 and the photoconductor (contactobject). The escaped toner and the additives abrade the edge 61 of thecleaning blade 5, and the cleaning capability under cool and dryconditions is degraded.

Additionally, hardness is generally likely to decrease as elastic powerincreases. If the elastic power of the edge layer 6 is 90% or greater,the edge layer 6 tends to be low, and it is possible that the edge 61wears as the edge 61 is drawn in by the photoconductor. Therefore, theelastic power of the edge layer 6 is preferably smaller than 90%.

Additionally, the elastic power of the backup layer 7 is preferably 70%or greater.

By setting the elastic power of the backup layer 7 to 70% or greater,fatigue of the cleaning blade 5 caused by plastic deformation of thebackup layer 7 is inhibited.

If the elastic power of the backup layer 7 is smaller than 70%, thebackup layer 7 plastically deforms, and the entire cleaning blade 5fatigues. Then, the line pressure decreases, resulting in defectivecleaning.

Although an upper limit is not specified in the elastic power of thebackup layer 7 according to an example embodiment, the elastic power oftypical urethane rubber is smaller than 95%.

Experiment 2

In Experiment 2, regarding the cleaning blades of Configurations 1through 4 and Comparative examples 1 through 8 described in Experiment1, Martens hardness was measured, and the occurrence of filming wasevaluated.

[Martens Hardness]

Martens hardness is calculated concurrently with calculation of elasticpower.

Similar to calculation of elastic power, the Martens hardness ismeasured as follows. Push a Vickers penetrator in the cleaning blade 5at 20 μm from the edge (ridgeline), with a strength of 1.0 mN for 10seconds, keep that state for 5 seconds, and gradually draws out theVickers penetrator in 10 seconds. Then, measure the Martens hardness.

As illustrated in FIG. 4, in the double-layer cleaning blade 5, if theedge layer 6 is extremely thin compared with the backup layer 7, it ispossible that the measurement value is affected by the Martens hardnessof the backup layer 7 when the Martens hardness of the edge layer 6 ismeasured from the opposing face 62.

For example, in measurement of the Martens hardness of the edge layer 6higher than the Martens hardness of the backup layer 7, if affected bythe Martens hardness of the backup layer 7, the measured Martenshardness of the edge layer 6 is lower than the measurement valueobtained by measuring the Martens hardness of the material used for theedge layer 6 alone.

The inventors have found that, even if the edge layer 6 is extremelythin compared with the backup layer 7, the Martens hardness of the edgelayer 6 can be measured with a higher degree of accuracy in thefollowing method.

Referring to FIG. 4, define the Martens hardness of the edge layer 6measured from the opposing face 62 (in the direction indicated by arrowEa) as Martens hardness A, define the Martens hardness of the edge layer6 measured from the end face 63 (in the direction indicated by arrow Eb)as Martens hardness B, and define the Martens hardness of the backuplayer 7 measured from the end face 63 (in the direction indicated byarrow Ec) as Martens hardness C. Calculate the difference betweenMartens hardness A and Martens hardness C, and that between Martenshardness B and Martens hardness C, and define, the greater of Martenshardness A or Martens hardness B in absolute value of the differencewith Martens hardness C, is determined as the Martens hardness of theedge layer 6. That is, when the absolute value of the difference betweenMartens hardness A and Martens hardness C is greater than the differencebetween Martens hardness B and Martens hardness C, Martens hardness A isdefined as the Martens hardness of the edge layer 6. When the differencebetween Martens hardness B and Martens hardness C is greater than thedifference between Martens hardness A and Martens hardness C, Martenshardness B is defined as the Martens hardness of the edge layer 6.

Table 2 shows the Martens hardness measured by this method.

[Evaluation Items]

(Occurrence of Filming)

Under a temperature of 32° C. and a humidity of 54%, a solid imageextending entirely A4 size was output on 10,000 sheets consecutively.The solid image was used to input a greater amount of toner to thephotoconductor. Then, the occurrence of filming was evaluated in thefollowing two levels.

None: The trace of filming on the output images is not observed witheyes, and image failure is not recognized.

Occurred: The trace of filming on the output images is observed witheyes, and the image is degraded.

TABLE 2 Elastic Martens hardness Blade power (%) (N/mm²) struc- EdgeBackup Edge Backup Fatigue ture layer layer layer layer of blade FilmingE1 Double 82 91 1.1 0.8 None None layer E2 Double 79 85 2.0 0.7 NoneNone layer E3 Double 75 81 2.5 0.9 None None layer E4 Double 72 89 3.50.7 None None layer E5 Double 69 92 4.1 0.7 None None layer E6 Double 6785 4.2 0.8 None None layer E7 Double 65 87 4.7 0.8 None None layer E8Double 62 82 5.0 0.9 None None layer E9 Double 58 92 5.4 0.7 None Nonelayer E10 Double 52 85 5.8 0.7 None None layer E11 Double 48 71 5.9 0.9None None layer E12 Double 46 80 6.1 0.9 None None layer E13 Double 4375 6.3 0.8 None None layer E14 Double 40 70 6.5 0.9 None None layer C1Single 92 0.7 None Oc- layer curred C2 Single 38 6.0 Fatigued None layerC3 Double 92 68 0.7 2.9 Fatigued Oc- layer curred C4 Double 87 59 0.84.0 Fatigued Oc- layer curred C5 Double 82 52 0.9 5.5 Fatigued Oc- layercurred C6 Double 78 48 2.1 6.3 Fatigued None layer C7 Double 30 80 7.00.9 None None layer C8 Double 35 85 6.8 0.9 None None layer C9 Double 3960 6.5 4.0 Fatigued None layer C10 Double 30 50 7.0 5.3 Fatigued Nonelayer

(Configuration 1)

In the cleaning blade 5 according to Configuration 1, the Martenshardness of the edge layer 6 is 1.1 N/mm², and the Martens hardness ofthe backup layer 7 is 0.8 N/mm². The Martens hardness of the edge layer6 is greater than 1.0 N/mm².

Configuration 1 was effective in inhibiting filming, meaning aphenomenon in which toner additives firmly adhere to the surface of theimage bearer. Making the edge 61 of the cleaning blade 5 relatively hardis advantageous in scraping off substances adhering to the surface ofthe contact object, thereby inhibiting inconveniences, such as filing,caused by the substances firmly adhering to the surface of the contactobject.

The edge layer 6 having a Martens hardness of equal to or greater than1.0 N/mm² is effective in inhibiting filming as follows.

FIGS. 11A, 11B, and 11C are illustrations of wear of the edge 261 of thecleaning blade 105.

If the Martens hardness of the edge 261 is smaller than 1.0 N/mm², thefollowing inconvenience may arise when the edge 261 of the cleaningblade 105 abuts or contacts the surface of the contact object 110 thatmoves in the direction indicated by arrow Y1, as illustrated in FIG.11A.

If the Martens hardness of the edge 261 is smaller than 1.0 N/mm²,deformation of the edge 261 caused by the load increases. Then, the areaof contact between the edge 261 and the contact object 110 and the widthof the nip therebetween increase.

Additionally, since the edge 261 is soft, as illustrated in FIG. 11B,the amount by which the edge 261 is drawn in by the movement of thecontact object 110 increases, and the edge 261 deforms greatly. When thenip between the contact object 110 and the edge 261 is large in widthand the amount of deformation of the edge 261 is large, the contactpressure of the edge 261 is dispersed. Then, the edge 261 fails toremove substances adhering to the contact object 110. Additionally, whenthe amount of deformation of the edge 261 is large, a load is applied tothe edge 261, causing abrasion and chipping as illustrated in FIG. 11C.

In the cleaning blade 5 according to Configuration 1, the Martenshardness of the edge layer 6 is equal to or greater than 1.0 N/mm². Thisstructure reduces the amount of deformation of the edge 61 caused by theload applied to the edge 61, and the area of contact between the edge 61and the contact object 110 and the width of the nip therebetween aremade smaller. Additionally, since the edge 61 is harder, the amount bywhich the edge 61 is drawn in by the movement of the photoconductor(contact object) is smaller, and the edge 61 less easily deforms. Whenthe width of the nip and the amount of deformation of the edge 61 aresmaller, the contact of the edge 261 with the contact object is stable.Then, the edge 61 reliably removes substances adhering to the contactobject. Additionally, since the deformation of the edge 61 is smaller,the load on the edge 61 is smaller. Accordingly, abrasion and chippingof the ridgeline at the end of the cleaning blade 5 are inhibited.

It is to be noted that, if the Martens hardness of the edge layer 6 isequal to or greater than 10 N/mm², the following inconvenience mayarise.

Generally, regarding urethane rubber used for cleaning blades, theelastic power tends to decrease as the hardness increases. Accordingly,as the cleaning blade becomes harder, the elastic power thereofdecreases. In the case of the cleaning blade reduced in elastic power,the edge of the cleaning blade plastically deforms (micro deformation)due to the sliding with the contact object, and the edge wears.Therefore, the Martens hardness of the edge layer 6 is preferablysmaller than 10 N/mm².

In the cleaning blade 5 according to Configuration 1, the edge layer 6is higher in Martens hardness than the backup layer 7.

When urethane rubber, which is widely used in cleaning blades, isincreased in hardness to enhance the capability to remove the substancesadhering to the contact object, elasticity thereof decreases. Then, thecapability to follow the surface unevenness of the contact objectdecreases. When the capability to follow decreases, the amount of tonerescaping the cleaning blade increases, and the cleaning capability isdegraded.

When the edge layer 6 is higher in Martens hardness than the backuplayer 7 as in Configuration 1, the capability of the edge layer 6 can beseparated from that of the backup layer 7. In other words, even in acase where the edge layer 6 is higher in hardness to enhance thecapability to clean the surface of the contact object, the capability ofthe entire cleaning blade to follow the surface shape of the contactobject is maintained by setting the hardness of the backup layer 7 to arelatively low value to secure the elasticity.

(Configurations 2 through 14)

Configurations 2 through 14 was effective in inhibiting filming of toneradditives on the surface of the image bearer since the Martens hardnessof the edge layer 6 was equal to or greater than 1.0 N/mm² similar toConfiguration 1.

Additionally, since the edge layer 6 was higher in Martens hardness thanthe backup layer 7, even in the case where the edge layer 6 wasincreased in hardness to enhance the cleaning capability, the capabilityof the entire cleaning blade to follow the surface shape of the contactobject was maintained.

The reason of such an evaluation result is similar to that ofConfiguration 1, and thus the description is omitted.

Comparative Example 1

In the Comparative example 1, the single-layer cleaning blade 105 wasused, and the Martens hardness of the edge 261 is lower than 1.0 N/mm².

Since the Martens hardness of the edge 261 was lower than 1.0 N/mm², thenip between the contact object 110 and the edge 261 was large in width,and the contact pressure of the edge 261 was dispersed. Accordingly, theedge 261 failed to remove substances adhering to the contact object 110.Additionally, since the amount of deformation of the edge 261 was large,the load was applied to the edge, causing abrasion and chipping. Thedispersion of contact pressure and the abrasion and chipping of the edge261 caused filming.

Comparative Example 2

In the Comparative example 2, the single-layer cleaning blade 105 wasused, and the Martens hardness of the edge 261 was 6.0 N/mm².

Generally, urethane rubber used for cleaning blades tends to decrease inelastic power as the hardness thereof increases. Accordingly, if thecleaning blade is made harder to inhibit filming, the elastic powerthereof decreases.

The cleaning blade 105 according to Comparative example 2 issingle-layered and made of the material higher in hardness and lower inelastic power. Accordingly, the rate of plastic deformation relative tothe elastic deformation is greater when the cleaning blade 105 isdeformed with force. Accordingly, the cleaning blade 105 according toComparative example 2 fatigued.

Comparative Examples 3 Through 5

The cleaning blade used in any of Configurations 3 through 5 isdouble-layered and includes the edge layer 6 and the backup layer 7.Differently from Configurations 1 through 14, the Martens hardness ofthe edge layer 6 is smaller than 1.0 N/mm².

Since the Martens hardness of the edge was lower than 1.0 N/mm², the nipbetween the contact object and the edge was large in width, and thecontact pressure of the edge was dispersed. Accordingly, the edge failedto remove substances adhering to the contact object. Additionally, sincethe amount of deformation of the edge was large, the load was applied tothe edge, causing abrasion and chipping. The dispersion of contactpressure and the abrasion and chipping of the edge caused filming.

Comparative Example 6

The cleaning blade used in Configuration 6 is double-layered andincludes the edge layer 6 and the backup layer 7. Differently fromConfigurations 1 through 14, the backup layer 7 is higher in Martenshardness than the edge layer 6.

Configuration 6 was effective in inhibiting filming since the Martenshardness of the edge layer 6 was equal to or greater than 1.0 N/mm².However, since the backup layer 7 was higher in Martens hardness thanthe edge layer 6, the elasticity of the entire cleaning blade decreased.Accordingly, the capability to follow decreased, and the amount of tonerescaping the cleaning blade increased, resulting in defective cleaning.

Comparative Examples 7 and 8

In the cleaning blade according to any of Comparative examples 7 and 8,the Martens hardness of the edge layer 6 is equal to or greater than 1.0N/mm². Similar to Configurations 1 through 14, the edge layer 6 ishigher in Martens hardness than the backup layer 7.

Since the Martens hardness of the edge layer 6 was equal to or greaterthan 1.0 N/mm², filming was inhibited.

Comparative Examples 9 and 10

In the cleaning blade according to Comparative example 9 or 10, theMartens hardness of the edge layer 6 is equal to or greater than 1.0N/mm². Similar to Configurations 1 through 14, the edge layer 6 ishigher in Martens hardness than the backup layer 7. Accordingly, filmingwas inhibited.

In the cleaning blade according to Comparative example 9 or 10, theelastic power of the backup layer 7 is smaller than 70%. Accordingly,the cleaning blade fatigued, and cleaning was defective.

Next, an electrophotographic printer is described below as an embodimentof an image forming apparatus incorporating the cleaning blade 5illustrated in FIG. 1. A basic configuration of the image formingapparatus is described below.

FIG. 5 is a schematic diagram of an image forming apparatus 100according to an example embodiment.

The image forming apparatus 100 is capable of forming multicolor imagesand includes an image forming unit 120, an intermediate transfer unit160, and a sheet feeder 130. It is to be noted that reference charactersY, C, M, and Bk show yellow, magenta, cyan, and black, respectively, andmay be omitted in the description below when color discrimination is notnecessary.

The image forming unit 120 includes process cartridges 121Y, 121C, 121M,and 121Bk for yellow, cyan, magenta, and black, respectively. Theprocess cartridges 121Y, 121C, 121M, and 121Bk are arranged in line in asubstantially horizontal direction. The process cartridges 121 areremovably insertable into the image forming apparatus 100.

The intermediate transfer unit 160 includes an intermediate transferbelt 162, which is an endless belt, primary transfer rollers 161Y, 161C,161M, and 161Bk, and a secondary transfer roller 165. The intermediatetransfer belt 162 is entrained around multiple support rollers. Theintermediate transfer belt 162 is positioned above the processcartridges 121 and along the direction in which drum-shapedphotoconductors 10Y, 10C, 10M, and 10Bk (i.e., latent image bearers) ofthe process cartridges 121Y, 121C, 121M, and 121Bk rotate. Theintermediate transfer belt 162 rotates in synchronization with therotation of the photoconductors 10. The primary transfer rollers 161 arepositioned along the inner circumferential side of the intermediatetransfer belt 162. With the primary transfer rollers 161, the outercircumferential face of the intermediate transfer belt 162 is lightlypressed against the surfaces of the photoconductors 10.

The process cartridges 121 are similar in configuration and operation toform toner images on the respective photoconductors 10 and transfer thetoner images onto the intermediate transfer belt 162. A pivot mechanismis provided for the three primary transfer rollers 161Y, 161C, and 161Mcorresponding to the process cartridges 121Y, 121C, and 121 M for colorsother than black to move these primary transfer rollers 161 verticallyin FIG. 5. The pivot mechanism disengages the intermediate transfer belt162 from the photoconductors 10Y, 10C, and 10M when multicolor imageformation is not performed. Additionally, a belt cleaning device 167 isdisposed downstream from the secondary transfer roller 165 and upstreamfrom the process cartridge 121Y in the direction indicated by arrow Y2shown in FIG. 5, in which the intermediate transfer belt 162 rotates.

Above the intermediate transfer unit 160, toner cartridges 159 for therespective process cartridges 121 are arranged substantiallyhorizontally. Below the process cartridges 121, an exposure device 140is provided. The exposure device 140 directs laser beams to the chargedsurfaces of the photoconductors 10 to form electrostatic latent imagesthereon.

The sheet feeder 130 is provided below the exposure device 140. Thesheet feeder 130 includes sheet trays 131 for containing sheets ofrecording media and sheet feeding rollers 132. The sheet feeder 130feeds sheets to a secondary transfer nip formed between the intermediatetransfer belt 162 and the secondary transfer roller 165 via a pair ofregistration rollers 133 at a predetermined timing.

A fixing device 30 is provided downstream from the secondary transfernip in the direction in which sheets are transported (hereinafter “sheetconveyance direction”). Further, an ejection roller and an output tray135 to receive sheets discharged are disposed downstream from the fixingdevice 30 in the sheet conveyance direction.

FIG. 6 schematically illustrates a configuration of the processcartridge 121 included in the image forming apparatus 100.

The process cartridges 121 have a similar configuration, and thereforethe subscripts Y, C, M, and Bk for color discrimination are omitted inthe description of the configuration and operation of the processcartridges 121, given below.

In addition to the drum-shaped photoconductor 10, the process cartridge121 includes a cleaning device 1, a charging device 40, and a developingdevice 50 disposed around the photoconductor 10.

The cleaning device 1 includes the elastic cleaning blade 5, which isshaped like a strip and long in the axial direction of thephotoconductor 10. The cleaning device 1 presses the edge 61(ridgeline), which is perpendicular to the rotation of thephotoconductor 10, to the surface of the photoconductor 10. With theedge 61 pressed against the surface of the photoconductor 10, thecleaning device 1 removes substances, such as residual toner, from thesurface of the photoconductor 10. A discharge screw 43 of the cleaningdevice 1 discharges the removed toner outside cleaning device 1.

The charging device 40 includes a charging roller 41 opposing thephotoconductor 10 and a roller cleaner 42 that rotates while beingcontact with the charging roller 41.

The developing device 50 is designed to supply toner to the surface ofthe photoconductor 10 to develop the latent image formed thereon into avisible image and includes a developing roller 51 serving as a developerbearer to bear developer including carrier and toner. The developingdevice 50 includes the developing roller 51, an agitation screw 52, anda supply screw 53. The agitation screw 52 stirs and transports developercontained in a developer container, and the supply screw 53 transportsthe developer while supplying the agitated developer to the developingroller 51.

The four process cartridges 121 having the above-described configurationcan be independently removed from the apparatus body, installed therein,and replaced by service persons or users. When the process cartridge 121is removed from the image forming apparatus 100, the photoconductor 10,the charging device 40, the developing device 50, and the cleaningdevice 1 can be replaced independently. It is to be noted that theprocess cartridge 121 may further includes a waste-toner tank to collectthe toner removed by the cleaning device 1. In this case, it isconvenient when the waste-toner tank is independently removable,installable, and replaceable.

Next, operation of the image forming apparatus 100 is described below.

The image forming apparatus 100 receives print commands via a controlpanel or from external devices such as computers. Initially, thephotoconductor 10 starts rotating in the direction indicated by arrow Ashown in FIG. 6, and the charging rollers 41 charge the surfaces of thephotoconductors 10 uniformly to a predetermined polarity. The exposuredevice 140 directs light, such as laser beams, for respective colors tothe charged photoconductors 10. The laser beams are optically modulatedaccording to multicolor image data input to the image forming apparatus100. Thus, electrostatic latent images for respective colors are formedon the photoconductors 10. The developing rollers 51 of developingdevices 50 supply respective color toners to the electrostatic latentimages, thereby developing the electrostatic latent images into tonerimages.

Subsequently, the transfer voltage opposite in polarity to the tonerimage is given to the primary transfer roller 161, thereby forming aprimary transfer electrical field between the photoconductor 10 and theprimary transfer roller 161 via the intermediate transfer belt 162.Simultaneously, the primary transfer nip is formed by the primarytransfer roller 161 lightly pressed against the intermediate transferbelt 162. With these actions, the respective toner images on thephotoconductors 10 are primarily transferred onto the intermediatetransfer belt 162 efficiently. The toner images are superimposed one onanother on the intermediate transfer belt 162, forming a multilayertoner image (i.e., multicolor toner image).

Toward the multilayer toner image on the intermediate transfer belt 162,a sheet is timely transported from the sheet tray 131 via the sheetfeeding roller 132 and the pair of registration rollers 133. A transfervoltage opposite in polarity to toner images is given to the secondarytransfer roller 165, thereby forming a secondary-transfer electricalfield between the intermediate transfer belt 162 and the secondarytransfer roller 165 via the sheet. The toner image is transferred ontothe sheet by the secondary-transfer electrical field. The sheet is thentransported to the fixing device 30, in which the toner image is fixedon the sheet with heat and pressure. The sheet bearing the fixed tonerimage is discharged by the ejection roller to the output tray 135. Afterthe primary-image transfer, toner remaining on the respectivephotoconductors 10 is removed by the cleaning blades 5 of the cleaningdevices 1.

It is to be noted that another embodiment employs a contact-typecharging roller to apply, to the image bearer, superimposed voltageincluding direct current (DC) voltage and alternating current (AC)voltage. In this configuration, the charging current is greater, and thepotential of the charged image bearer becomes more reliable, thusenhancing image quality and extending the operational life.

When the AC voltage is applied to a charger, the image bearer vibrates,and the edge 61 of the cleaning blade 5 vibrates significantly. Thevibration causes noise and wear or chipping of the cleaning blade 5 andaggravates wear of the photoconductor 10. In the cleaning blade 5according to an example embodiment, the edge layer 6 is lower in elasticpower than the backup layer 7. Accordingly, an example embodimentsuppresses noise, wear, and chipping of the cleaning blade 5 as well asaggravated wear of the photoconductor 10 caused by vibration due to ACvoltage applied to the charger.

Next, descriptions are given below of another configuration of theprocess cartridge to which the cleaning blade 5 according to an exampleembodiment is applied.

FIG. 7 is a schematic cross-sectional view illustrating a processcartridge 122 installable in the image forming apparatus 100 accordingto an example embodiment.

The process cartridge 122 includes a lubrication device 70 to supplyprotectant, as lubricant, to the surface of the photoconductor 10. Thecharging roller 41 used in the process cartridge 122 is either incontact or contactless with the photoconductor 10 to charge thephotoconductor 10, and AC voltage is applied to the charging roller 41.The lubrication device 70 is disposed downstream from the cleaningdevice 1 in the direction indicated by arrow A, in which thephotoconductor 10 rotates. With this arrangement, the protectant isreliably applied to the photoconductor 10.

In the lubrication device 70, a bar-shaped solid protectant 72 is heldby a cylindrical support 71. A compression spring 73 disposed inside thesupport 71 biases the solid protectant 72 to the photoconductor 10. Arotatable foamed urethane roller 77 is disposed between the solidprotectant 72 and the photoconductor 10. By rotating, the foamedurethane roller 77 scrapes off protectant from the solid protectant 72and applies the protectant to the surface of the photoconductor 10.Downstream from the foamed urethane roller 77 in the direction indicatedby arrow A, an application blade 75 made of or includes polyurethane orthe like is disposed to level the protectant in a thin layer on thesurface of the photoconductor 10.

The foamed urethane roller 77 rotates in a direction counter to rotationof the photoconductor 10 indicated by arrow A. The application blade 75contacts the photoconductor 10 in a direction trailing to rotation ofthe photoconductor 10. With this arrangement, the protectant can beeffectively made into a thin layer without being scraping off thephotoconductor 10.

The protectant used here includes fatty acid metallic salt and inorganiclubricant. In such protectant, since the fatty acid metallic salt isbroken by the charging current, damage of the surface of thephotoconductor 10 is inhibited. Simultaneously, with the inorganiclubricant that is not broken by the charging current, lubricatingcapability of the protectant is maintained in a better conditioncompared with applying the fatty acid metallic salt only. Accordingly,more preferable cleaning of the photoconductor 10 is attained.

Examples usable as fatty acid metallic salt include, but not limited to,barium stearate, lead stearate, iron stearate, nickel stearate, cobaltstearate, copper stearate, strontium stearate, calcium stearate, cadmiumstearate, magnesium stearate, zinc stearate, zinc oleate, magnesiumoleate, iron oleate, cobalt oleate, copper oleate, lead oleate,manganese oleate, zinc palmitate, cobalt palmitate, lead palmitate,magnesium palmitate, aluminum palmitate, calcium palmitate, leadcaprylate, lead caprate, linolenic acid, zinc linolenate, cobaltlinolenate, calcium linolenate, zinc ricinoleate, and cadmiumricinoleate; and a mixture thereof. Two or more of these materials canbe used in combination. Among these materials, zinc stearate isparticularly preferable for its suitability for film formation on thephotoconductor 10.

Inorganic lubricant is an inorganic compound that cleaves by itself andlubricates a target or causes slip therein. Specific examples include,but not limited to, talc, mica, boron nitride, molybdenum disulfide,tungsten disulfide, kaolin, smectite, hydrotalcite compounds, calciumfluoride, graphite, planar alumina, sericite, and synthetic mica. Amongthese materials, in boron nitride, hexagonal net faces in which atomsare firmly combined together overlays with each other with relativelywide spaces secured between layers, and only Van der Waals force, whichis relatively weak, acts between the layers. Thus, boron nitride easilycleaves and lubricates the target, and thus boron nitride isparticularly preferable. It is to be noted that, to give hydrophobicitythereto, inorganic lubricant can be subjected to surface treatment asrequired.

Experiment 3

Descriptions are given below of Experiment 3 executed to evaluate thedouble-layer cleaning blade 5 (illustrated in FIG. 1) including the edgelayer 6 of elastic power smaller than 40%. In Experiment 3, cleaningcapability under cool and dry conditions were evaluated with thelubricated photoconductor 10 and the photoconductor 10 not lubricatedwhile the elastic powers of the edge layer 6 and the backup layer 7 werechanged.

(Defective Cleaning Under Cool and Dry Conditions)

A Ricoh image forming apparatus, MP C3503, was used as a test machine,and the cleaning blade 5 of the process cartridge 122 illustrated inFIG. 7 was replaced with those according to Configurations 15 through 18and Comparative examples 11 through 14. The evaluations were made usingboth of the photoconductor 10 lubricated and the photoconductor 10 notlubricated.

Under cool and dry conditions, defective cleaning is likely to occur.After the test machine was left unused for 24 houses under lowtemperature (10° C.) and low humidity (15%) conditions, images wereoutput on 80,000 sheets consecutively under the temperature of 10° C.and the humidity of 15%. To input a greater amount of toner to thephotoconductor 10 (image bearer), a solid image extending entirely A4size was input. The output sheets were checked for a trace of defectivecleaning with eyes and evaluated as follows.

Not observed: Cleaning capability is good. After output of 80,000sheets, the trace of defective cleaning is not observed on the sheets,and practically there are no problems.

Observed: The trace of defective cleaning is visible. After output of80,000 sheets, the trace of defective cleaning was observed on thesheets, and practically the outputs images were deemed substandard.

Table 3 below shows evaluation results of Configurations 15 through 18(E15 through E18 in Table 3) and the Comparative examples (C11 throughC14 in Table 3).

TABLE 3 Elastic power (%) Cleaning capability Blade Edge Backup undercool and structure layer layer Lubrication dry conditions E15 Double 3071 Lubricated Good layer E16 Double 32 90 Lubricated Good layer E17Double 35 82 Lubricated Good layer E18 Double 38 85 Lubricated Goodlayer C11 Double 30 71 Not Defective layer lubricated C12 Double 32 90Not Defective layer lubricated C13 Double 35 82 Not Defective layerlubricated C14 Double 38 85 Not Defective layer lubricated

(Configuration 15)

In Configuration 15 (E15 in Table 3), the double-layer cleaning blade 5including the edge layer 6 and the backup layer 7 was used. In thecleaning blade 5 according to Configuration 15, the backup layer 7 ishigher in elastic power than the edge layer 6, and the elastic power ofthe edge layer 6 is equal to or greater than 30% and smaller than 40%.

When the elastic power of the edge layer 6 is smaller than 40%, the edge61 of the cleaning blade 5 plastically deforms (micro deformation) dueto the sliding with the photoconductor 10. The plastic deformationincreases the amount of toner escaping the cleaning blade 5, and theedge 61 wears as the amount of escaping toner increases. Accordingly,cleaning becomes defective.

In Configuration 15, lubricant was applied to the surface of thephotoconductor 10, thereby reducing the friction between the cleaningblade 5 and the photoconductor 10.

Reducing the friction is effective in reducing the load applied to theedge 61 of the cleaning blade 5, and wear of the edge 61 is inhibited.Accordingly, defective cleaning under cool and dry was inhibited.

(Configurations 16 through 18)

In the cleaning blades 5 according to any of Configurations 16 through18, the elastic powers of the edge layer 6 and the backup layer 7 aredifferent from those of Configuration 15 as shown in Table 3. Similar toConfiguration 15, the elastic power of the edge layer 6 is equal to orgreater than 30% and smaller than 40%, and lubricant was applied to thesurface of the photoconductor 10, thereby inhibiting degradation ofcleaning capability. The reason of such an evaluation result is similarto that of Configuration 15, and thus the description is omitted.

Comparative Example 11

In the cleaning blade used in Comparative example 11, the backup layer 7is higher in elastic power than the edge layer 6 similar toConfiguration 15. However, the photoconductor 10 was not lubricated.When the elastic power of the edge layer 6 is smaller than 40% and thephotoconductor 10 is not lubricated, the friction between thephotoconductor 10 and the cleaning blade 5 increases, and the edge 61 ofthe cleaning blade 5 plastically deforms (micro deformation) due to thesliding with the photoconductor 10. The plastic deformation increasesthe amount of toner escaping the cleaning blade 5, and the edge 61 wearsas the amount of escaping toner increases. Accordingly, cleaning undercool and dry conditions was defective due to the wear of the edge 61 ofthe cleaning blade 5.

Comparative Examples 12 and 13

Similar to comparative example 1, the elastic power of the edge layer 6was smaller than 40%, and lubricant was not applied to the surface ofthe photoconductor 1. Accordingly, cleaning was defective due to thewear of the edge 61 of the cleaning blade 5. The reason of suchevaluation is similar to that of Comparative example 11, and thus thedescription is omitted.

From the evaluation results shown in Table 3, lubricating the contactobject, namely, the photoconductor 10, is preferable. With the lubricantapplied to the photoconductor 10, the friction between the cleaningblade 5 and the photoconductor 10 is reduced, and the load applied tothe edge 61 of the cleaning blade 5 is reduced, thereby inhibiting wearof the edge 61 of the cleaning blade 5. Accordingly, defective cleaningunder cool and dry conditions is inhibited.

When the photoconductor 10 is lubricated, it is preferable that the edgelayer 6 of the cleaning blade 5 has an elastic power of 30% or greater.With this structure, even in configurations where the elastic power ofthe edge layer 6 is smaller than 40%, defective cleaning caused byplastic deformation of the edge 61 is inhibited.

It is to be noted that, in Experiment 3, urethane rubber having anelastic power of 30% or greater was used to maintain elasticity of thematerial. When the elastic power of the edge layer 6 is smaller than30%, it is difficult to maintain the elasticity of the material.

Next, descriptions are given below of yet another configuration of theprocess cartridge to which the cleaning blade 5 according to an exampleembodiment is applied.

FIG. 8 is a schematic cross-sectional view illustrating a processcartridge 123.

The process cartridge 123 employs a spring compression to press thecleaning blade 5 to the surface of the photoconductor 10. Specifically,the process cartridge 123 includes a pressing device 80 using a spring81. The spring compression used in the process cartridge 123 is constantcontact-pressure type and keeps the contact pressure of the cleaningblade 5 to the photoconductor 10 constant, regardless with elapse oftime.

The pressing device 80 includes a rotation support 82, serving as afulcrum, provided to the support 3 to support the cleaning blade 5. Thepressing device 80 causes the support 3 to rotate or pivot around therotation support 82 by the tension of the spring 81, thereby pressingthe edge 61 of the cleaning blade 5 to the photoconductor 10. It is tobe noted that, in the structure illustrated in FIG. 8, the pressingforce of the edge 61 is set at 20.0 g/cm.

The charging roller 41 used in the process cartridge 123 is in contactwith the photoconductor 10 to charge the photoconductor 10, and ACvoltage is applied to the charging roller 41. The charging roller 41uniformly charges the surface of the photoconductor 10 by rotating whilebeing in contact with the photoconductor 10.

Experiment 4

Descriptions are given below of Experiment 4 to evaluate the cleaningblade 5 including the backup layer 7 of elastic power smaller than 70%.In Experiment 4, effects of wear of the cleaning blade 5 on the cleaningcapability were evaluated while the elastic powers of the edge layer 6and the backup layer 7 as well as the pressing type to press thecleaning blade 5 were changed.

(Cleaning Blade Pressing Type)

Using the process cartridge 123 illustrated in FIG. 8, the constantcontact-pressure type and a constant biting-amount type were evaluatedas the pressing type of the cleaning blade 5. In the constantcontact-pressure type, the contact pressure of the cleaning blade 5 tothe photoconductor 10 is kept constant by the spring 81 even with elapseof time. In the constant biting-amount type, the support 3 illustratedin FIG. 8 was secured to keep the amount by which the edge 61 of thecleaning blade 5 bites in the photoconductor 10 (hereinafter “bitingamount of the cleaning blade 5”) by 0.8 mm to 1.1 mm, thereby keepingthe biting amount of the cleaning blade 5 substantially constant.

(Fatigue of Blade)

In experiment 4, the Ricoh image forming apparatus, MP C3503, was used,and the cleaning blade 5 of the process cartridge 123 illustrated inFIG. 8 was replaced with those according to Configurations 19 through 22and Comparative examples 15 and 16.

Using the test machine, the blade edge contact pressure was measuredbefore and after the cleaning blade was kept in contact with thephotoconductor 10 for seven days (168 hours) under a temperature of 23°C. and a humidity of 50% (ordinary room conditions). The cleaning bladewas kept in contact with the photoconductor 10, and changes in contactpressure were evaluated while the cleaning blade was kept under thepressure. The cleaning blade was set to contacts the photoconductor 10with a contact pressure of 20 g/cm.

Effects of fatigue of the cleaning blade on the cleaning capability wereevaluated as follows under a condition of high charging current.

Not affected: Reduction in line pressure is smaller than 4.0 g/cm (20%of line pressure setting). No effects on the cleaning capability.

Affected: Reduction in line pressure is equal to or greater than 4.0g/cm (20% of line pressure setting). Cleaning capability affected.

Evaluation results of configurations according to an example embodimentand the comparative examples are shown in Table 4 below.

TABLE 4 Fatigue of blade Line Elastic power (%) pressure Blade EdgeBackup Pressing Effects on change structure layer layer type cleaning(g/cm) E19 Double 59 69 Constant Not 0.5 layer contact affected pressureE20 Double 50 61 Constant Not 0.4 layer contact affected pressure E21Double 46 55 Constant Not 0.5 layer contact affected pressure E22 Double41 50 Constant Not 0.7 layer contact affected pressure C15 Double 53 66Constant Affected 4.8 layer biting amount C16 Double 42 53 ConstantAffected 5.3 layer biting amount

In Table 4, E19 through E22 represent Configurations 19 through 22, andC15 and C16 represent Comparative examples 15 and 16.

(Configuration 19)

In Configuration 19, the double-layer cleaning blade 5 including theedge layer 6 and the backup layer 7 illustrated in FIG. 1 was used. Inthe cleaning blade 5 according to Configuration 19, the backup layer 7is higher in elastic power than the edge layer 6, and the elastic powerof the backup layer 7 is equal to or greater than 50% and smaller than70%.

As the elastic power of the backup layer 7 decreases, the cleaning blade5 is more likely to deform plastically due to the bending stress appliedto the cleaning blade 5, and the cleaning blade 5 is more likely tofatigue. In the constant biting-amount type, when the cleaning blade 5fatigues, the biting amount of the cleaning blade 5 is constant orsubstantially constant, and accordingly the line pressure decreases,making cleaning defective.

By contrast, the pressing type in Configuration 19 is not the constantbiting-amount type but the constant contact-pressure type using thepressing device 80 illustrated in FIG. 8. In the constantcontact-pressure type, the contact pressure is constant regardless ofelapse of time, and the line pressure does not decrease even when thecleaning blade 5 fatigues. Thus, the defective cleaning due to decreasesin line pressure is less likely to occur. In Configuration 19, the linepressure decreased by 0.4 g/cm, which is relatively small, and thus thecleaning capability was not significantly degraded.

(Configurations 20 Through 22)

In the cleaning blades 5 according to any of Configurations 20 through22, the elastic powers of the edge layer 6 and the backup layer 7 aredifferent from those of Configuration 1 as shown in Table 4. Other thanthat, the Configurations 20 through 22 are similar to Configuration 19.

In Configurations 20 through 22, the decrease in the line pressure wasrelatively small and from 0.4 g/cm to 0.6, and thus the cleaningcapability was not significantly degraded. The reason of such anevaluation result is similar to that of Configuration 19, and thus thedescription is omitted.

Comparative Example 15

In the cleaning blade used in Comparative example 15, the backup layer 7is higher in elastic power than the edge layer 6 similar toConfiguration 19, and the elastic power of the backup layer 7 is equalto or greater than 50% and smaller than 70%. However, differently fromConfigurations 19 through 22, the biting amount of the cleaning blade 5was kept constant.

As the elastic power of the backup layer 7 decreases, the cleaning blade5 is more likely to deform plastically due to the bending stress appliedto the cleaning blade 5, and the cleaning blade 5 is more likely tofatigue. In the constant biting-amount type, the line pressure decreasesas the cleaning blade 5 fatigues with elapse of time, and cleaningbecomes defective.

The line pressure was reduced by 4.1 g/cm after the cleaning blade waskept in contact with the photoconductor 10 for 168 hours. This reductionin line pressure is greater than the specified line pressure reductionof 4.0 g/cm (20% of line pressure setting), which causes defectivecleaning in MP C3503. This reduction in line pressure reduction degradedthe cleaning capability.

Comparative Example 16

In the cleaning blade according to Comparative example 16, the elasticpower of the backup layer 7 is 50% or greater and smaller than 70%similar to Comparative example 15. However, in Comparative example 16,the biting amount of the cleaning blade 5 was kept constant, and thusthe line pressure decreased with elapse of time, making cleaningdefective. The reason of such evaluation is similar to that ofComparative example 16, and thus the description is omitted.

From the evaluation results shown in Table 4, it is preferable to keepthe contact pressure of the cleaning blade 5 constant. When the pressureconstant is kept constant, even when the cleaning blade 5 fatigues withelapse of time, the line pressure is kept constant or substantiallyconstant. Accordingly, the defective cleaning due to decreases in linepressure is inhibited.

Additionally, when the constant contact-pressure type is employed, theelastic power of the backup layer 7 is preferably 50% or greater. Withthis structure, even when the elastic power of the backup layer 7 issmaller than 70%, decreases in line pressure are inhibited.

Next, the photoconductor 10 serving as the image bearer used in theembodiment is described below.

FIGS. 9A through 9D are cross-sectional views of layer structuresapplicable to the photoconductor 10 according to an example embodiment.In the layer structure illustrated in FIG. 9A, the photoconductor 10includes a conductive support 91 and a photosensitive layer 92 overlyingthe conductive support 91, and inorganic particles are present at oradjacent to the surface of the photosensitive layer 92. The layerstructure illustrated in FIG. 9B includes, from the bottom, theconductive support 91, the photosensitive layer 92, and a surface layer93 including inorganic particles. The layer structure illustrated inFIG. 9C includes, from the bottom, the conductive support 91, thephotosensitive layer 92, and the surface layer 93 including inorganicparticles. The photosensitive layer 92 includes a charge generationlayer 921 and a charge transport layer 922. The layer structureillustrated in FIG. 9D includes, from the bottom, the conductive support91; a under layer 94; the photosensitive layer 92 including the chargegeneration layer 921 and the charge transport layer 922; and the surfacelayer 93 including inorganic particles.

That is, the photoconductor 10 according to an example embodimentincludes, above the conductive support 91, at least the photosensitivelayer 92, and the surface layer 93 may be provided above thephotosensitive layer 92. In another embodiment, one or more layers arecombined freely.

As illustrated in FIG. 92A, when the photosensitive layer 92 serves asthe surface layer, the photosensitive layer 92 includes inorganicparticles. When the photosensitive layer 92 includes the chargegeneration layer 921 and the charge transport layer 922 superimposedthereon, and the charge transport layer 922 is the surface layer, andthe charge transport layer 922 includes inorganic particles.

Examples of inorganic particles added to the layer structure includemetal powder such as copper, tin, aluminum, and indium; metal oxide suchas silicon oxide, silica, tin oxide, zinc oxide, titanium oxide, indiumoxide, antimony oxide, bismuth oxide, tin oxide in which antimony isdoped, and indium oxide in which tin is doped; and inorganic materialsuch as potassium titanate. Metal oxide is particularly preferable, andfurther silicon oxide, aluminum oxide, and titanium oxide are effective.

The inorganic particle preferably has an average primary particlediameter from 0.01 to 0.5 μm considering the characteristics of thesurface layer 93 such as light transmission degree and abrasionresistivity. The abrasion resistivity and the degree of dispersiondecrease when the average primary particle diameter is 0.01 μm orsmaller. Additionally, when the average primary particle diameter is 0.5μm or greater, inorganic particles in the dispersion liquid can sinkmore easily, and toner filming can occur.

As the amount of inorganic particles added increases, abrasionresistivity increases, which is desirable. An extremely large amount ofinorganic particles, however, causes side effects such as increases inresidual potentials and decreases in the degree at which writing lighttransmits a protective layer. Generally, the amount of addition to thetotal solid amount is preferably 30% by weight or less, and morepreferably 20% by weight or less. The lower limit is generally 3% byweight.

The above-described inorganic particles can be treated with at least onesurface treatment agent, which is preferable for facilitating thedispersion of inorganic particles.

Degradation in dispersion of inorganic particles can cause not only therise of residual potentials but also degradation of transparency ofcoating, defective coating, and further degradation of abrasionresistivity. Accordingly, degradation in dispersion of inorganicparticles can hinder the extension of operational life or image qualityimprovement. Next, the photosensitive layer 92 is described below.

In the layer structure illustrated in FIGS. 9B, 9C, and 9D, thephotoconductor 10 includes, above the photosensitive layer 92, thesurface layer 93 including inorganic particles.

The surface layer 93 includes at least inorganic particles and binderresin. Examples of inorganic particle include powder of metal such ascopper, tin, aluminum, and indium; metal oxide such as silicon oxide,silica, tin oxide, zinc oxide, titanium oxide, indium oxide, antimonyoxide, bismuth oxide, tin oxide in which antimony is doped, indium oxidein which tin is doped; and inorganic materials such as potassiumtitanate. Metal oxide is particularly preferable, and further siliconoxide, aluminum oxide, and titanium oxide are effective.

The inorganic particle preferably has an average primary particlediameter from 0.01 to 0.5 μm considering the characteristics of thesurface layer 93 such as light transmission degree and abrasionresistivity.

The abrasion resistivity and the degree of dispersion decrease when theaverage primary particle diameter is 0.01 μm or smaller. Additionally,when the average primary particle diameter is 0.5 μm or greater,inorganic particles in the dispersion liquid can sink more easily, andtoner filming can occur. When the amount of inorganic particles added tothe surface layer 93 is large, abrasion resistivity is high, which isdesirable. An extremely large amount of inorganic particles, however,causes side effects such as increases in residual potentials anddecreases in the degree at which writing light transmits the protectivelayer.

Generally, the amount of addition to the total solid amount ispreferably 50% by weight or less, and more preferably 30% by weight orless. The lower limit is generally 3% by weight.

The above-described inorganic particles can be treated with at least onesurface treatment agent, which is preferable for facilitating thedispersion of inorganic particles.

Degradation in dispersion of inorganic particles can cause not only therise of residual potentials but also degradation of transparency ofcoating, defective coating, and further degradation of abrasionresistivity. Accordingly, degradation in dispersion of inorganicparticles can hinder the extension of operational life or image qualityimprovement. Typical surface treatment agents can be used, but surfacetreatment agents capable of maintaining insulation of inorganicparticles are preferable.

For example, titanate coupling agents, aluminum coupling agents,zircoaluminate coupling agents, higher fatty acids, mixtures of silanecoupling agents and those, Al2O3, TiO2, ZrO2, silicone, aluminumstearate, and mixtures of two or more of them are preferable as thesurface treatment agent to attain preferable dispersion of inorganicparticles and inhibition of image blurring.

Although treatment with silane coupling agents increases image blurringeffects, the effects may be inhibited by mixing the above-describedsurface treatment agents in the silane coupling agent. The amount ofsurface treatment agent is preferably from 3% by weight to 30% by weightand, more preferably, from 5% by weight to 20% by weight although itdepends on the average primary particle diameter of inorganic particle.If the amount of surface treatment agent is smaller than this range,dispersion of inorganic particles is insufficient. If the amount isextremely large, the residual potential can rise significantly. Theabove-mentioned inorganic particles can be used alone or in combination.The above-mentioned inorganic particles can be dispersed using adispersing device. The average particle diameter of the inorganicparticles in the dispersion liquid is preferably 1 μm or smaller and,more preferably, 0.5 μm or smaller considering the transmittance of thesurface layer 93.

As described above with reference to FIGS. 9A through 9C, includinginorganic particles in the surface layer 93 (or the photosensitive layer92 in FIG. 9A) is advantageous in inhibiting increases in friction forceby the contact of the cleaning blade 5 with the photoconductor 10, andwear resistance of the surface of the photoconductor 10 is enhanced. Asthe wear resistance of the surface of the photoconductor 10 is enhanced,uneven wear (partial wear) is alleviated, thereby enhancing imagequality, reliability, and durability of the electrophotographic imageforming apparatus 100.

Additionally, the inorganic particles at the surface of thephotoconductor 10 create micro surface unevenness, and it is possiblethat the edge 61 of the cleaning blade 5 vibrates, causing noise, wearor chipping of the cleaning blade 5, and aggravated wear of thephotoconductor 10. In an example embodiment, since the cleaning blade 5includes the edge layer 6 lower in elastic power than the backup layer7, noise, wear and chipping of the cleaning blade 5, and aggravated wearof the photoconductor 10 are inhibited.

Next, descriptions are given below of toner preferably used in imageforming apparatuses adopting feature of this specification.

FIGS. 10A and 10B are illustrations of measurement of circularity oftoner.

To improve image quality, it is preferable to use polymerization tonerproduced by suspension polymerization, emulsion polymerization, ordispersion polymerization, which is suitable for enhancing circularityand reducing particle diameter. In particular, it is preferred to usepolymerization toner having a circularity of 0.97 or higher and a volumeaverage particle diameter of 5.5 μm or smaller. High resolution can beattained by use of polymerization toner having a circularity of 0.97 orhigher and a volume average particle diameter of 5.5 μm or smaller.

The circularity used herein is an average circularity measured by aflow-type particle image analyzer FPIA-2000 from SYSMEX CORPORATION.Specifically, put surfactant as a dispersant, preferably 0.1 ml to 0.5ml of alkylbenzene sulfonate, in 100 ml to 150 ml of water from whichimpure solid materials are previously removed, and add 0.1 g to 0.5 g ofthe sample (toner) to the mixture. Then, disperse the mixture includingtoner with an ultrasonic disperser for 1 to 3 minutes to prepare adispersion liquid having a concentration of from 3,000 to 10,000pieces/μl, and measure the toner shape and distribution with theabove-mentioned measurer. Based on the measurement results, obtain L2/L1wherein L1 represents a peripheral length of a projected toner particlehaving an area S illustrated in FIG. 10A, and L2 represents a peripherallength of a perfect circle illustrated in FIG. 10B, identical in areawith the projected toner particle. The average thereof is used as thecircularity.

The volume average particle diameter of toner can be measured by acoulter counter method. Specifically, number distribution and volumedistribution of toner, measured by Coulter Multisizer 2e from BeckmanCoulter, are output, via an interface from Nikkaki Bios Co., Ltd., to acomputer and analyzed.

More specifically, the volume average particle diameter of toner isobtained as follows. Prepare, as an electrolyte, a NaCl aqueous solutionincluding a primary sodium chloride of 1%. Add 0.1 ml to 5 ml ofsurfactant, preferably alkylbenzene sulfonate, as dispersant, to 100 mlto 150 ml of the electrolyte. Add, as test sample, 2 to 20 mg of tonerto the mixture and disperse the test sample by an ultrasonic disperserfor 1 to 3 min. Put 100 ml to 200 ml of the electrolyte solution in aseparate beaker, and put the above-described sample therein to attain apredetermined concentration. Then, using Coulter Multisizer 2e, measurethe particle diameter of 50,000 toner particles with an aperture of 100μm.

The number of channels used in the measurement is thirteen. The rangesof the channels are from 2.00 μm to less than 2.52 μm, from 2.52 μm toless than 3.17 μm, from 3.17 μm to less than 4.00 μm, from 4.00 μm toless than 5.04 μm, from 5.04 μm to less than 6.35 μm, from 6.35 μm toless than 8.00 μm, from 8.00 μm to less than 10.08 μm, from 10.08 μm toless than 12.70 μm, from 12.70 μm to less than 16.00 μm, from 16.00 μmto less than 20.20 μm, from 20.20 μm to less than 25.40 μm, from 25.40μm to less than 32.00 μm, from 32.00 μm to less than 40.30 μm. The rangeto be measured is set from 2.00 μm to less than 40.30 μm. The target istoner particles of particle diameter greater than 2.00 μm and equal toor smaller than 32.0 μm.

Calculate the volume average particle diameter represented as ΣXfV/ΣfV,wherein X represents a representative diameter in each channel, Vrepresents an equivalent volume of the representative diameter in eachchannel, and f represents the number of particles in each channel.

The configurations described above are just examples, and each of thefollowing aspects of this specification attains a specific effect.

Aspect A: Aspect A concerns an elastic blade, such as the cleaning blade5, which includes a contact edge (ridgeline at an end), such as the edge61, to contact a surface of a contact object. The blade includes an edgelayer that includes the contact edge, and at least one backup layerlaminated on the edge layer. The elastic power of the layer(s) of theblade other than the edge layer is greater in elastic power than theedge layer.

According to Aspect A, as described above, regarding plastic deformationcaused by force of bending or compression applied to the cleaning blade5, the amount of plastic deformation of the backup layer 7 is smallerthan the amount of plastic deformation of the edge layer 6. Accordingly,even in a configuration where the edge layer 6 has a greater hardness,fatigue of the entire cleaning blade 5 is suppressed.

Additionally, as the cleaning blade 5 slidingly contacts thephotoconductor 10, the edge 61 of the cleaning blade 5 vibrates (microvibration). If the frequency of this vibration coincides with theeigenfrequency of the cleaning blade 5, the vibration of the edge layer6 including the edge 61 is about to grow. At that time, the backup layer7 greater in elastic power than the edge layer 6 absorbs the vibrationof the edge layer 6, thus serving as a vibration isolator. Accordingly,the backup layer 7 suppresses the occurrence of noise inherent to microvibration of the edge 61 caused by the sliding with the contact object.

Further, since the edge layer 6 is lower in elastic power than thebackup layer 7, the backup layer 7 absorbs the vibration caused bydeformation of the edge layer 6, and the vibration frequency of the edgelayer 6 less easily coincides with the eigenfrequency of the cleaningblade 5. Accordingly, the occurrence of vibration inherent in recoveryfrom deformation of the edge 61 is inhibited.

Aspect B: In Aspect A, the elastic power of the layer or layers (thebackup layer 7) other than the edge layer 6 is measured from the side ofthe blade end face (i.e., the end face 63) adjoining the opposing facevia the contact edge (i.e., the edge 61) and is 70% or greater.

According to Aspect B, as described with reference to the results of theexperiments, the fatigue of the blade is suppressed by plasticdeformation of the backup layer.

If the elastic power of the backup layer is smaller than 70%, the backuplayer plastically deforms due to bending stress given to the blade, andthe entire blade fatigues. Then, the line pressure decreases. In thecase of the cleaning blade 5, cleaning becomes defective.

Aspect C: In Aspect A or B, the elastic power of the layer or layers(the backup layer 7) other than the edge layer 6 measured from the bladeend face (end face 63) is greater than either the elastic power of theedge layer measured from the blade end face or the elastic power of theedge layer measured from the opposing face. According to this aspect, asdescribed above, even if the edge layer 6 is extremely thin comparedwith the backup layer 7, the elastic power of the edge layer 6 can bemeasured with a higher degree of accuracy. Accordingly, the elasticpower of the edge layer 6 is properly compared with that of the backuplayer 7.

Aspect D: In any of Aspects A through C, the elastic power of the edgelayer 6 measured from either the opposing face (62) or the blade endface (end face 63) is 40% or greater.

As described with reference to the results of the experiments, thisaspect is advantageous in inhibiting defective cleaning caused byplastic deformation of the contact edge of the blade. If the elasticpower of the edge layer 6 is smaller than 40%, micro plastic deformationof the edge 61 occurs due to the sliding with the contact object. Then,a greater amount of substances (e.g., toner and additives) escape fromthe gap at the nip between the contact edge and the contact object. Theescaped substances abrade the contact edge of the blade, and thecleaning capability is degraded.

Aspect E: In any of Aspects A through D, the contact object such as thephotoconductor 10 is lubricated with lubricant such as the protectantsupplied from the solid protectant 72.

As described with reference to the results of the experiments, thisaspect reduces the friction between the blade and the contact object,and the load applied to the contact edge of the blade is reduced,thereby inhibiting wear of the contact edge. Accordingly, defectivecleaning under cool and dry is inhibited.

Aspect F: In any of Aspects A through C, the contact object such as thephotoconductor 10 is lubricated with lubricant such as the protectantsupplied from the solid protectant 72, and the elastic power of the edgelayer is 30% or greater.

As described with reference to the results of the experiments, with thisaspect, even when the elastic power of the edge layer 6 is smaller than40%, inconveniences caused by plastic deformation of the contact edge 61is inhibited.

Aspect G: In any of Aspects A through F, a pressing device (80) pressesthe blade to the contact object with a contact pressure of the bladewith the contact object kept constant or substantially constant.

According to this aspect, the contact pressure is kept constantregardless of elapse of time, and the line pressure does not decrease.Accordingly, the defective cleaning due to decreases in line pressure isinhibited.

Aspect H: In any of Aspects A through E, the pressing device (80)presses the blade to the contact object with a contact pressure of theblade with the contact object kept constant or substantially constant,and the elastic power of the layer(s) of the blade other than the edgelayer is 50% or greater.

As described with reference to the results of the experiments, with thisaspect, even when the elastic power of the backup layer is smaller than70%, inconveniences caused by line pressure reduction is inhibited.

Aspect I: In Aspect A, the Martens hardness of the edge layer is equalto or greater than 1.0 N/mm².

As described with reference to the results of the experiments, thisaspect is advantageous in inhibiting firm adhesion of toner additive tothe image bearer (i.e., filming).

When the Martens hardness of the edge layer is lower than 1.0 N/mm², thenip between the contact object and the contact edge is large in width,and the contact pressure of the contact edge is dispersed. Accordingly,the edge failed to remove substances adhering to the contact object.Additionally, since the amount of deformation of the contact edge islarge, the load applied to the contact edge is large, causing abrasionand chipping of the contact edge. The filming occurs due to thedispersion of contact pressure and the abrasion and chipping of thecontact edge cause.

Aspect J: In Aspect I, the edge layer is greater in Martens hardnessthan the layer(s) of the blade other than the edge layer.

According to this aspect, as described with reference to the results ofthe experiments, the function of the edge layer is separated from thefunction of the backup layer. In other words, even in a case where theedge layer is higher in hardness to enhance the capability to clean thesurface of the contact object, the capability of the entire cleaningblade to follow the surface shape of the contact object is maintained bysetting the hardness of the backup layer to a relatively low value tosecure the elasticity.

Aspect K: In Aspect I or J, the Martens hardness of the edge layer,measured from either the side of the opposing face or the side of theblade end face, is greater than the Martens hardness of the layer(s) ofthe blade other than the edge layer, measured from the blade end face.

According to this aspect, as described above, even if the edge layer 6is extremely thin compared with the backup layer 7, the Martens hardnessof the edge layer 6 can be measured with a higher degree of accuracy.Accordingly, the Martens hardness of the edge layer 6 is properlycompared with that of the backup layer 7.

Aspect L: An image forming apparatus includes a charger, such as thecharging device 40, to charge a surface of an image bearer, such as thephotoconductor 10; an exposure device (140) to expose the surface of thecharged image bearer to form an electrostatic latent image thereon; adeveloping device (50) to develop the latent image with toner into avisible image; a transfer device, such as the intermediate transfer unit160 and the secondary transfer roller 165 to transfer the toner imageonto a recording medium; a fixing device (30) to fix the toner image onthe recording medium; and a cleaning device (1) to remove toner from theimage bearer. The cleaning device includes the blade according to anyone of Aspects A through K.

This aspect inhibits fatigue of the entire blade of the cleaning deviceas well as noise caused by vibration of the edge layer that contacts thephotoconductor.

Aspect M: In Aspect L, the charger such as the charging device 40applies AC voltage to the surface of the image bearer such as thephotoconductor 10.

According to this aspect, the potential of the charged image bearerbecomes more stable, thus enhancing image quality and extending theoperational life.

Aspect N: In Aspect L, the image bearer such as the photoconductor 10includes inorganic particles at the surface thereof.

According to this aspect, the wear of the image bearer is inhibited,thereby enhancing image quality, reliability, and durability of theelectrophotographic image forming apparatus.

Aspect O: An image forming apparatus includes a charger, such as thecharging device 40, to charge a surface of an image bearer, such as thephotoconductor 10; an exposure device (140) to expose the surface of thecharged image bearer to form an electrostatic latent image thereon; adeveloping device (50) to develop the latent image with toner into atoner image; a transfer device, such as the intermediate transfer unit160 and the secondary transfer roller 165 to transfer the toner imageonto a recording medium; a fixing device (30) to fix the toner image onthe recording medium; and a cleaning device (1) to remove toner from theimage bearer, and a lubrication device (70) to lubricate the surface ofthe image bearer; and the cleaning device includes the blade accordingto any one of Aspects E or F.

Numerous additional modifications and variations are possible in lightof the above teachings. It is therefore to be understood that, withinthe scope of the appended claims, the disclosure of this patentspecification may be practiced otherwise than as specifically describedherein.

1.-14. (canceled)
 15. An elastic blade comprising: an edge layerincluding a contact edge to contact a contact object and an opposingface to oppose the contact object; at least one backup layer laminatedon the edge layer and being greater in elastic power than the edgelayer; and a blade end face adjoining the opposing face via the contactedge, wherein an elastic power of the at least one backup layer measuredfrom the blade end face is 70% or greater.
 16. The blade according toclaim 15, further comprising a blade end face adjoining the opposingface via the contact edge, wherein an elastic power of the at least onebackup layer measured from the blade end face is greater than an elasticpower of the edge layer measured from either the blade end face or theopposing face.
 17. The blade according to claim 15, further comprising ablade end face adjoining the opposing face via the contact edge, whereinan elastic power of the edge layer measured from either the opposingface or the blade end face is 40% or greater.
 18. The blade according toclaim 15, wherein the edge layer has a Martens hardness of 30% orgreater, and the contact edge is to contact a lubricated surface of thecontact object.
 19. The blade according to claim 15, wherein the edgelayer has a Martens hardness of 1.0 N/mm² or greater.
 20. The bladeaccording to claim 19, wherein the edge layer is greater in Martenshardness than the at least one backup layer.
 21. The blade according toclaim 19, further comprising a blade end face adjoining the opposingface via the contact edge, wherein a Martens hardness of the edge layermeasured from either the opposing face or the blade end face is greaterthan a Martens hardness of the at least one backup layer measured fromthe blade end face.
 22. A cleaning device comprising: the bladeaccording to claim 15; and a pressing device to press the blade to thecontact object, wherein the pressing device keeps a contact pressure ofthe blade with the contact object constant.
 23. The blade according toclaim 22, wherein the at least one backup layer has an elastic power of50% or greater.
 24. An image forming apparatus comprising: an imagebearer serving as the contact object; a charger to charge a surface ofthe image bearer; an exposure device to expose the surface of thecharged image bearer to form an electrostatic latent image thereon; adeveloping device to develop the latent image with toner into a tonerimage; a transfer device to transfer the toner image onto a recordingmedium; a fixing device to fix the toner image on the recording medium;and a cleaning device to remove toner from the image bearer, thecleaning device including the blade according to claim
 15. 25. The imageforming apparatus according to claim 24, wherein the charger applies ACvoltage to the surface of the image bearer.
 26. The image formingapparatus according to claim 24, wherein the image bearer comprisesinorganic particles at the surface thereof.
 27. An image formingapparatus comprising: an image bearer serving as the contact object; acharger to charge a surface of the image bearer; an exposure device toexpose the surface of the charged image bearer to form an electrostaticlatent image thereon; a developing device to develop the latent imagewith toner into a toner image; a transfer device to transfer the tonerimage onto a recording medium; a fixing device to fix the toner image onthe recording medium; a cleaning device to remove toner from the imagebearer, the cleaning device including the blade according to claim 15;and a lubrication device to lubricate the surface of the image bearer,wherein the edge layer has an elastic power of 30% or greater.